X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ms-smtp-05.texas.rr.com ([24.93.47.44] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2201453 for flyrotary@lancaironline.net; Thu, 26 Jul 2007 22:12:44 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.93.47.44; envelope-from=clouduster@austin.rr.com Received: from [10.0.0.99] (cpe-70-113-77-184.austin.res.rr.com [70.113.77.184]) by ms-smtp-05.texas.rr.com (8.13.6/8.13.6) with ESMTP id l6R2BgnH006111 for ; Thu, 26 Jul 2007 21:11:43 -0500 (CDT) Message-ID: <46A9545D.3060905@austin.rr.com> Date: Thu, 26 Jul 2007 21:11:41 -0500 From: Dennis Haverlah User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Oil cooler inlet - what next? References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------090306000803020401070504" X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. --------------090306000803020401070504 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Ed, How can a person determine if the oil cooler is "saturated"? Thanks, Dennis H. Ed Anderson wrote: > Sorry to hear your efforts produced no noticeable improvement, Al. > > I do have a question - what is the core volume of your oil cooler? A > stock 2 rotor color has a core area of approx 19x4/12x2 = 171 Cubic > Inches. That will cool a two rotor at 160 mph producing 160 Hp with > an oil BTU heat factor of 2688 BTU/min. A 3 rotor producing 1/3 more > HP (213 HP) rpm would create a corresponding rise in BTU/min to 3360. > > Is your core big enough to dissipate that much increase? Sorry, I > just can't remember what size oil cooler you have. > > The reason I ask, is that if forcing more air through the core does > not decrease the oil temp - could there exist the possibility that > the core is saturated and can is simply not capable of transferring > more oil heat to the air? If that were the case, then, as you know, > no amount of additional air through the core would make any > significant difference. > > > Ed > > > > > > --- Original Message ----- > > From: Al Gietzen > To: Rotary motors in aircraft > Sent: Thursday, July 26, 2007 7:06 PM > Subject: [FlyRotary] Re: Oil cooler inlet - what next? > > Installed sheet metal 'baffle' to form new upper wall of the > diffuser as shown in the photo. The idea was to assist in > maintaining attached flow, and to block leakage through the gap at > the top. The baffle was done in 3 pieces in order to insert past > the divider/supports in the scoop; each piece is about 7 ½" wide. > There are gaps between pieces of about 3/8 - ½" inch. The inlet > pressure probe was placed at point "D". > > > > Test flight showed no noticeable difference in delta T on the > oil. The pressure measured at "D" was 3" H2O. Pressure behind > the exit fairing was again -3/4". The pressures at C and D > (measured at different times) are at about 6" from the inboard end > of the 22" long cooler. There may be some variation axially. > Because of the gaps in the baffle, and fitting around the end > tanks, there is still some air bypassing the cooler; but I don't > know how significant. Given the 9+" H2O dynamic pressure out in > front of the scoop still indicates not good pressure recovery. > > > > Nonetheless; it is certainly disappointing that there was no > change (within the accuracy of the temp measurements) in the > effective cooling. This suggests that the wall shape and the air > leakage are not the problem. > > > > Calculating back from the temp changes in oil and air suggest > there is only about 1000 cfm going through the cooler core. The > extrapolation of my measured data on air flow vs pressure drop > across the core suggests that at 3" H2O there should be about 2000 > cfm through the core. Because of the centrifugal blower I was > using for flow tests I was only able to get data up to about 0.6" > H2O and 700 cfm. I fit the data to Y=ax+bx2 using regression > analysis, which gave a very good fit up to that point; but > extrapolating out to 3" may be stretching it. If I assume the > pressure drop goes as the cube of the flow velocity, the > extrapolation is considerable different - about 1330 cfm at 3" H2O. > > > > Al > > > > > > -----Original Message----- > From: Rotary motors in aircraft > [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen > Sent: Friday, July 20, 2007 10:42 AM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: Oil cooler inlet > > > > Well; I may end up with VGs and change in upper duct wall shape. > My intention yesterday was to install VGs as a first step, test > fly, measure pressure and temps; then proceed with installing > sheet metal upper duct wall change. > > > > In deciding where to put the VGs, I looked at things with the gear > up (Photo 1). The gear door has a bump, and there is some gap > around the door. Don't know what all this does to BL. Ended up > putting VG toward the left side about 26" in font of scoop, and > toward the right side right on the gear door bump. > > > > I then spent a bunch of time trying to get the pressure measuring > tube situated. The only access is through the scoop opening, and > I can't get my hands in there; so it is very tough. Plus the tube > going in there, or along the surface in front will affect the flow > behavior, so what affect are we going to measure. Having multiple > measurements would be great; but very difficult to achieve. > > > > While doing that, I spent some time looking in there with a small > mirror. What I noted was that initial gaps above and below the > cooler (required to slide the unit in and out) had changed a bit. > The cooler is supported on pads of 'Cool-Mat' insulation. Those > have compressed just a little, so now there is very little gap at > the bottom, and 1/8"+ along the top. That is a fairly substantial > leak, and the loss of pressure at the top likely exacerbates the > flow separation. I decided it wasn't worth going to test the VGs > as long as that leakage gap was there. > > > > Taking the wing off (mostly getting it back on because of next to > impossible access to nuts), and removing the cooler looks a bit > much right now. I realized then; that by putting in a sheet metal > 'false' upper duct wall, I could extend it up into the gap at the > top (photo 2), thereby changing the shape, and (mostly) closing > the gap at the top. > > > > The false wall has to be in three parts for the three openings, > and there will be gaps between because of the supporting dividers; > but it could make a substantial difference. I made the piece for > the center, and considered testing just that; but the upper gap > concerns me enough that I think I'll try to get all three fit in. > > > > Then go take a flight test. Unfortunately this combines three > changes, VGs, closing gap, and changing duct wall. I had hoped to > test these one at a time. If there is a substantial change; it > will be easy to remove the VGs to see what that effect was. > > > > Of course I'll let you know when I get some results. > > > > Oh, the price of innovationJ. > > > > Al > > > > > > -----Original Message----- > From: Rotary motors in aircraft > [mailto:flyrotary@lancaironline.net] On Behalf Of Thomas Jakits > Sent: Thursday, July 19, 2007 10:31 AM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: Oil cooler inlet > > > > Okay, > > > > Monty thinks the emphasis is on the BL. > > I believe (don't know), the main-problem is the upper ductwall > shape. Even if you have perfect BL flow, the upper wall shape is > still not good and will stall the flow. > > At the end of the game you want good flow at all speeds and be > able to close any ducts to limit excess cooling (when you > hopefully get there). > > Obviously BL will play a role in your installation as the intake > is rather narrow. > > However BL or not - BL does not mean there is no flow, just slower > and more turbulent, but still generally going towards the cooler. > > Aerodynamics in the duct should be much the same for laminar, > turbulent, any flow, as long as there is flow. > > When things stall is when flow pretty much ceases (in the stalled > area ....), no matter how well things where at the entrance. > > The stall in this case is rather "easy" to get, as the speed seems > rather low already. Still may be good enough if you can do away > with the stall. > > So I suggest to work on the duct wall first and optimize it. > > > > As suggested, with some kind of sheet, alu, fiberglass, etc. You > can curve it more and more until you peak. > > Maybe pinched ducts (copyright Ed!!) are not working here, but it > may as well - if they work a Ed's theory explains (energizes the > flow...) > > > > If this works, modify according to the best shape found. > > Then try to improve with VGs or sanding or turbolator tape. > > Then go for the exit - after all it is a differential pressure > game.... > > > > TJ > > > > On 7/18/07, M Roberts > wrote: > > Al, > > > > I think you need to do something to energize the boundary layer. > If you can't divert it you need to put some energy into it. It is > probably getting slow and separating from the face of the duct. > That is what your data seems to indicate to me. > > > > I like the shape that Thomas proposes better than what you have > now, however, I still think you will need some VG's in front of > the inlet. > > > > I know it may seem counter intuitive, but turbulence may actually > help in this case. You will not get very efficient internal > diffusion, but it will be a lot better than what you have now. I > don't think that putting a turning vane will help too much without > doing something to energize the boundary layer first. You'll just > have a slow thick low energy layer, and a high energy layer > separated by a turning vane. > > > > It is really easy to duct tape some aluminum VG's in front of the > inlet and see what it does. > > > > You may need a combination of Thomas' contour, VG's and a turning > vane. Go with the easy fix and work your way up in complexity. > > > > Monty > > > > ------------------------------------------------------------------------ > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > --------------090306000803020401070504 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Ed,

How can a person determine if the oil cooler is "saturated"? 

Thanks,
Dennis H.

Ed Anderson wrote:
Sorry to hear your efforts produced no noticeable improvement, Al.
 
I do have a question - what is the core volume of your oil cooler?  A stock 2 rotor color has a core area of approx 19x4/12x2 = 171 Cubic Inches.  That will cool a two rotor at 160 mph producing 160 Hp with an oil BTU heat factor of 2688 BTU/min.  A 3 rotor producing 1/3 more HP (213 HP) rpm would create a corresponding rise in BTU/min to 3360.
 
   Is your core big enough to dissipate that much increase?  Sorry, I just can't remember what size oil cooler you have.  
 
The reason I ask, is that if forcing more air through the core does not decrease the oil temp - could there  exist the possibility that the core is saturated and can is simply not capable of transferring more oil heat to the air?  If that were the case, then, as you know,  no amount of additional air through the core would make any significant difference.
 
 
Ed
 
 
 
 
 
--- Original Message -----
From: Al Gietzen
Sent: Thursday, July 26, 2007 7:06 PM
Subject: [FlyRotary] Re: Oil cooler inlet - what next?

 Installed sheet metal ‘baffle’ to form new upper wall of the diffuser as shown in the photo.  The idea was to assist in maintaining attached flow, and to block leakage through the gap at the top.  The baffle was done in 3 pieces in order to insert past the divider/supports in the scoop; each piece is about 7 ½” wide.  There are gaps between pieces of about 3/8 – ½” inch.  The inlet pressure probe was placed at point “D”.

 

Test flight showed no noticeable difference in delta T on the oil.  The pressure measured at “D” was 3” H2O.  Pressure behind the exit fairing was again -3/4”.  The pressures at C and D (measured at different times) are at about 6” from the inboard end of the 22” long cooler.  There may be some variation axially.  Because of the gaps in the baffle, and fitting around the end tanks, there is still some air bypassing the cooler; but I don’t know how significant.  Given the 9+” H2O dynamic pressure out in front of the scoop still indicates not good pressure recovery.

 

Nonetheless; it is certainly disappointing that there was no change (within the accuracy of the temp measurements) in the effective cooling.  This suggests that the wall shape and the air leakage are not the problem.

 

Calculating back from the temp changes in oil and air suggest there is only about 1000 cfm going through the cooler core. The extrapolation of my measured data on air flow vs pressure drop across the core suggests that at 3” H2O there should be about 2000 cfm through the core.  Because of the centrifugal blower I was using for flow tests I was only able to get data up to about 0.6” H2O and 700 cfm.  I fit the data to Y=ax+bx2 using regression analysis, which gave a very good fit up to that point; but extrapolating out to 3” may be stretching it.  If I assume the pressure drop goes as the cube of the flow velocity, the extrapolation is considerable different – about 1330 cfm at 3” H2O.

 

Al

 

 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Friday, July 20, 2007 10:42 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Oil cooler inlet

 

Well; I may end up with VGs and change in upper duct wall shape. My intention yesterday was to install VGs as a first step, test fly, measure pressure and temps; then proceed with installing sheet metal upper duct wall change.

 

In deciding where to put the VGs, I looked at things with the gear up (Photo 1).  The gear door has a bump, and there is some gap around the door.  Don’t know what all this does to BL.  Ended up putting VG toward the left side about 26” in font of scoop, and toward the right side right on the gear door bump.

 

I then spent a bunch of time trying to get the pressure measuring tube situated.  The only access is through the scoop opening, and I can’t get my hands in there; so it is very tough.  Plus the tube going in there, or along the surface in front will affect the flow behavior, so what affect are we going to measure.  Having multiple measurements would be great; but very difficult to achieve.

 

While doing that, I spent some time looking in there with a small mirror.  What I noted was that initial gaps above and below the cooler (required to slide the unit in and out) had changed a bit.  The cooler is supported on pads of ‘Cool-Mat’ insulation.  Those have compressed just a little, so now there is very little gap at the bottom, and 1/8”+ along the top.  That is a fairly substantial leak, and the loss of pressure at the top likely exacerbates the flow separation.  I decided it wasn’t worth going to test the VGs as long as that leakage gap was there.

 

Taking the wing off (mostly getting it back on because of next to impossible access to nuts), and removing the cooler looks a bit much right now.  I realized then; that by putting in a sheet metal ‘false’ upper duct wall, I could extend it up into the gap at the top (photo 2), thereby changing the shape, and (mostly) closing the gap at the top.

 

The false wall has to be in three parts for the three openings, and there will be gaps between because of the supporting dividers; but it could make a substantial difference.  I made the piece for the center, and considered testing just that; but the upper gap concerns me enough that I think I’ll try to get all three fit in.

 

Then go take a flight test. Unfortunately this combines three changes, VGs, closing gap, and changing duct wall.  I had hoped to test these one at a time.  If there is a substantial change; it will be easy to remove the VGs to see what that effect was.

 

Of course I’ll let you know when I get some results.

 

Oh, the price of innovationJ.

 

Al

 

 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Thomas Jakits
Sent: Thursday, July 19, 2007 10:31 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Oil cooler inlet

 

Okay,

 

Monty thinks the emphasis is on the BL.

I believe (don't know), the main-problem is the upper ductwall shape. Even if you have perfect BL flow, the upper wall shape is still not good and will stall the flow.

At the end of the game you want good flow at all speeds and be able to close any ducts to limit excess cooling (when you hopefully get there).

Obviously BL will play a role in your installation as the intake is rather narrow.

However BL or not - BL does not mean there is no flow, just slower and more turbulent, but still generally going towards the cooler.

Aerodynamics in the duct should be much the same for laminar, turbulent, any flow, as long as there is flow.

When things stall is when flow pretty much ceases (in the stalled area ....), no matter how well things where at the entrance.

The stall in this case is rather "easy" to get, as the speed seems rather low already. Still may be good enough if you can do away with the stall.

So I suggest to work on the duct wall first and optimize it.

 

As suggested, with some kind of sheet, alu, fiberglass, etc. You can curve it more and more until you peak.

Maybe pinched ducts (copyright Ed!!) are not working here, but it may as well - if they work a Ed's theory explains (energizes the flow...)

 

If this works, modify according to the best shape found.

Then try to improve with VGs or sanding or turbolator tape.

Then go for the exit - after all it is a differential pressure game....

 

TJ

 

On 7/18/07, M Roberts <montyr2157@alltel.net> wrote:

Al,

 

I think you need to do something to energize the boundary layer. If you can't divert it you need to put some energy into it. It is probably getting slow and separating from the face of the duct. That is what your data seems to indicate to me.

 

I like the shape that Thomas proposes better than what you have now, however, I still think you will need some VG's in front of the inlet.

 

I know it may seem counter intuitive, but turbulence may actually help in this case. You will not get very efficient internal diffusion, but it will be a lot better than what you have now. I don't think that putting a turning vane will help too much without doing something to energize the boundary layer first. You'll just have a slow thick low energy layer, and a high energy layer separated by a turning vane.

 

It is really easy to duct tape some aluminum VG's in front of the inlet and see what it does.

 

You may need a combination of Thomas' contour, VG's and a turning vane. Go with the easy fix and work your way up in complexity.

 

Monty

 

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